Add Annotations to POJO class generated at runtime

Question

I am using below code to generate POJO classes at runtime. I would like to Add annotations to this class, is it possible to add Class level annotations to the generated class or should I use any other solution to generate classes

import java.util.Map;

import org.springframework.cglib.beans.BeanGenerator;
import org.springframework.cglib.core.NamingPolicy;
import org.springframework.cglib.core.Predicate;

/**
 * @author dpoddar
 *
 */
public class DynamicClassUtils {

    public static Class<?> createBeanClass(
            final String className,
            final Map<String, Class<?>> properties){

        final BeanGenerator beanGenerator = new BeanGenerator();

        /* use our own hard coded class name instead of a real naming policy */
        beanGenerator.setNamingPolicy(new NamingPolicy(){
            @Override public String getClassName(final String prefix,
                    final String source, final Object key, final Predicate names){
                return className;
            }});

        beanGenerator.setUseCache(true);
        beanGenerator.setSuperclass(com.xxx.BaseDataImport.class);

        BeanGenerator.addProperties(beanGenerator, properties);
        return (Class<?>) beanGenerator.createClass();
    }
}

Answer 1

cglib is a rather old library and does not support annotations.

If you are open to an alternative, have a look at Byte Byddy (which I wrote). It is open-source and Apache-licensed and a more modern take on byte code generation where "newer" Java features like annotations were built into the generation API.

For creating a bean, you can define a class like:

Class<?> type = new ByteBuddy()
  .subclass(BaseDataImport.class)
  .name(name)
  .defineProperty("foo", String.class)
  .annotateType(annotation)
  .make()
  .load(classLoader)
  .getLoaded();

This would define a property foo of type String with getter and setter and annotate the class with the supplied annotation.